BoomGate: Deadlock Avoidance in Non-Minimal Routing for High-Radix Networks

Abstract

Avoiding routing deadlock is an important component of an interconnection network. For large-scale systems with high-radix topologies that leverage non-minimal adaptive routing, virtual channels (VCs) are commonly used to prevent routing deadlock. However, VCs in large-scale networks can be costly because of deep buffers and restrict VC usage. In this work, we propose BoomGATE for deadlock avoidance in large-scale networks. In particular, BoomGATE consists of two components-Restricted Intermediate-node Non-minimal Routing (RINR) algorithm and opportunistic flow control (OFC) which both exploit the low-diameter characteristics of high-radix networks while maximizing path diversity within the topology. We identify how routing deadlock in fully-connected topologies are caused by non-minimal routes and propose to restrict the non-minimal routing to ensure deadlock freedom without additional virtual channels. We also propose an algorithm that ensures path diversity is load-balanced across all nodes in the system. However, since path diversity is restricted with the RINR algorithm, complement RINR algorithm with opportunistic flow control (OFC) where 'illegal routes' are allowed if and only if sufficient buffer can be guaranteed to ensure cyclical dependency does not occur. We propose both a static and dynamic OFC implementation. We evaluate the performance of BoomGATE and demonstrate there is minimal performance loss compared to global adaptive routing, while reducing the amount of buffers required by 50%.